The telephone has existed as a primary means for communications throughout most of the 20th century. Telephone communications are characterized by point-to-point connections, in which a caller is connected to a receiver by, essentially, a dedicated channel through various switching systems. The channel can be any of a variety of media, including copper wire, optical fiber, satellite, cellular, and so on. The nature of such communication is well known in the art.
More recently, alternative forms of communication have developed. In particular, the communications network generally referred to as the Internet has come rapidly to prominence. Internet communications generally involve transfers of digital packets of information, which are transmitted between a sender and a receiver through one or more computers referred to as servers interconnected by high speed data links. Internet communications, however, can be distinguished from conventional telephone communications in that Internet communications typically are not point-to-point, but may be rerouted from server to server during file transfer.
Quite recently, techniques have been developed to provide at least rudimentary real-time voice communications across the Internet between suitably configured computer systems--i.e., a "telephone call" via the Internet. Such techniques include, typically, the use of a conventional telephone channel from the caller's computer system to its local Internet service provider, across the Internet to the local service provider for the receiver, and across a conventional telephone channel from the receiver's Internet service provider to the receiver's computer system. At least some of the techniques are believed to involve digitizing of the audio and formatting the digitized signal into packets, followed by packet transmission from the caller to the receiver. To maximize transmission speed, the UDP communications protocol is typically used, although this protocol trades off speed for reliability of communication. Suitable computers may include a Pentium-based system having a suitably sized hard disk, 28.8KBaud modem, and a sound card.
Unfortunately, virtually all voice communications techniques currently used on the Internet result in significant signal data loss or delays, resulting in unacceptably poor audio quality such as lost words or parts of words or noticeable delays between speakers. At least in part, this poor audio quality is due to lost or unduly delayed packets, such that the digitized signal cannot be reconstructed at the receiver's system. There has therefore been a need for a communications technique which permits audio signals to be transmitted over the Internet with acceptable audio quality.